Method of performing cell measurement and method of providing information for cell measurement

ABSTRACT

A method and base station for transmitting information for cell measurements, and a method and user equipment for performing cell measurements are discussed. The method according to one embodiment includes transmitting, by the base station, signals according to an almost blank subframe pattern; and transmitting, by the base station, information indicating a first time domain measurement resource restriction pattern and a second time domain measurement resource restriction pattern. The almost blank subframe pattern indicates which subframes the base station is configuring. The first time domain measurement resource restriction pattern indicates which subframe is one or more first subframes configured for reference signal received power (RSRP) or reference signal received quality (RSRQ) measurements, and the second time domain measurement resource restriction pattern indicates which subframe is one or more second subframes configured for RSRP or RSRQ measurements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending U.S. application Ser.No. 14/326,326 filed on Jul. 8, 2014, which is a Continuation of U.S.patent application Ser. No. 13/529,448 filed on Jun. 21, 2012 (now U.S.Pat. No. 8,787,194, issued on Jul. 22, 2014), which claims priorityunder 35 U.S.C. §119(e) to U.S. Provisional Application Nos. 61/531,082filed on Sep. 5, 2011, and 61/579,641 filed on Dec. 22, 2011, and whichalso claims priority under 35 U.S.C. §119(a) to Korean patentapplication No. 10-2012-0018204, filed on Feb. 22, 2012. The entirecontents of all these applications are hereby incorporated by referenceinto the present application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a method of performing cellmeasurement and a method of providing information for cell measurement.

2. Discussion of the Related Art

Recently, studies on a next-generation multimedia radio communicationsystem have been actively conducted. The radio communication systemrequires a system that can process various information including images,radio data, etc. in lieu of services mainly using voice and transmit theinformation. The object of the radio communication system enables aplurality of users to perform reliable communication regardless oflocation and mobility. However, wireless channels suffer from severalproblems such as path loss, shadowing, fading, noise, limited bandwidth,power limitation of terminals and inter-user interference. Otherchallenges in the design of the radio communication system includeresource allocation, mobility issues related to rapidly chancingphysical channels, portability and design for providing security andprivacy.

When a transmission channel suffers from deep fading, if another versionor replica of a signal transmitted to a receiver s not separatelytransmitted to the receiver, it is difficult for a receiver to determinethe transmitted signal. A resource corresponding the separate version orreplica is called as a diversity, and the diversity is one of the mostimportant factors contributing to reliable transmission. If thetransmission capacity or transmission reliability of data can bemaximized using the diversity, and a system for implementing a diversityusing multiple transmit and receive antennas is referred to as amultiple input multiple output (MIMO) system.

Techniques for implementing the diversity in the MIMO system are spacefrequency block code (SFBC), space time block code (STBC), cyclic delaydiversity (CDD), frequency switched transmit diversity (FSTD), timeswitched transmit diversity (TSTD), precoding vector switching (PVS),spatial multiplexing (SM), etc.

Meanwhile, one of systems considered after the 3rd generation system isan orthogonal frequency division multiplexing (OFDM) system capable ofreducing an inter-symbol interference effect with low complexity. TheOFDM system converts serially input data into N parallel data andtransmits the N parallel data respectively carried by N orthogonalsubcarriers. The subcarrier maintains orthogonality in terms offrequencies. Orthogonal frequency division multiple access (OFDMA)refers to Orthogonal Frequency Division Multiple Access (OFDMA) refersto a multiple access method of realizing multi-access by independentlyproviding users with some of available subcarriers in a system usingOFDM as a modulation method.

FIG. 1 illustrates a radio communication system.

Referring to FIG. 1, the radio communication system includes at leastone base station (BS) 20. Each of the BSs 20 provides a communicationservice for a specific terrestrial area (generally, referred to as acell) 20 a, 20 b or 20 c. The cell may be divided into a plurality ofareas (also referred to as sectors). A user equipment (UE) 10 may befixed or have mobility. The UE 10 may be called as other terms includinga mobile station (MS), a subscriber station (SS), a wireless device, apersonal digital assistant (PDA), a wireless modem, a handheld device,etc. The BS 20 generally refers to a fixed station communicating withthe UEs 10, and may be called as other terms including an evolved-NodeB(eNB), a base transceiver system, an access point, etc.

Hereinafter, downlink (DL) means communication from a BS to a UE, anduplink (UL) means communication from a UE to a BS. In the DL, atransmitter may be a portion of the BS and a receiver may be a portionof the UE. In the UL, a transmitter may be a portion of the UE and areceiver may be a portion of the BS.

The radio communication system may be any one of a multiple inputmultiple output (MIMO) system, a multiple input single output (MISO)system, a single input single output (SISO) system and a single inputmultiple output (SIMO). The MIMO system uses a plurality of transmitantennas and a plurality of receive antenna. The MISO system uses aplurality of transmit antennas and one receive antenna. The SISO systemuses one transmit antenna and one receive antenna. The SIMO system usesone transmit antenna and a plurality of receive antennas.

Hereinafter, the transmit antenna means a physical or logical antennaused to transmit one signal or stream, and the receive antenna means aphysical or logical antenna used to receive one signal or stream.

Meanwhile, a long term evolution (LTE) system defined by 3rd generationpartnership project (3GPP) employs the MIMO. Hereinafter, the LTE systemwill be described in detail.

FIG. 2 illustrates a structure of a radio frame in 3GPP LTE.

Referring to FIG. 2, the radio frame is composed of ten subframes, andone subframe is composed of two slots. The slots in the radio frame aredesignated by slot numbers from 0 to 19. The time at which one subframeis transmitted is referred to as a transmission time interval (TTI). TheTTI may be called as a scheduling unit for data transmission. Forexample, the length of one radio frame may be 10 ms, the length of onesubframe may be 1 ms, and the length of one slot may be 0.5 ms.

The structure of the radio frame is merely an example, and the number ofsubframes included in the radio frame, the number of slots included inthe subframe, etc. may be variously modified.

FIG. 3 is an exemplary view illustrating a resource grid for one UL slotin the 3GPP LTE.

Referring to FIG. 3, the UL slot includes a plurality of OFDM symbols ina time domain, and includes N^(UL) resource blocks (RBs) in a frequencydomain. The OFDM symbol is used to represent one symbol period, may becalled as an SC-FDMA symbol, OFDMA symbol or symbol period depending ona system. The BS includes a plurality of subcarriers in the frequencydomain as a resource allocation unit. The number N^(UL) of RBs includedin the UL slot depends on the UL transmission bandwidth configured in acell. Each element on a resource grid is referred to as a resourceelement.

Although it has been illustrated in FIG. 3 that one RB includes a 712resource element composed of 7 OFDM symbols in the time domain and 12subcarriers in the frequency domain, the number of subcarriers and thenumber of OFDM symbols in the RB are not limited thereto. The number ofOFDM symbols and the number of subcarriers in the RB may be variouslychanged. The number of OFDM symbols may be changed depending on thelength of a cyclic prefix (CP). For example, the number of OFDM symbolsin a normal CP is 7, and the number of OFDM symbols in an extended CP is6.

The resource grid for one UL slot in the 3GPP LTE of FIG. 3 may beapplied to the resource grid for one DL slot.

FIG. 4 illustrates a structure of a DL subframe.

The DL subframe includes two slots in the time domain, and each of theslots includes seven OFDM symbols in the normal CP. Maximum three OFDMsymbols (maximum four OFDM symbols for a bandwidth of 1.4 MHz) prior toa first slot in the subframe become a control region to which controlchannels are allocated, and the other OFDM symbols become a data regionto which a downlink shared channel (PDSCH) is allocated. The PDSCH meansa channel through which a BS transmits data to a UE.

A physical downlink control channel (PDCCH) may carry resourceallocation (also referred to as DL grant) and transmission format on adownlink-shared channel (DL-SCH), resource allocation information (alsoreferred to as UL grant) on a uplink-shared channel (UL-SCH), paginginformation on a paging channel (PCH), system information on the DL-SCH,resource allocation of an upper layer control message such as a randomaccess response transmitted on the PDSCH, a set of transmission powercontrol (TPC) for individual UEs in a UE group, activation of a voiceover Internet protocol (VoIP), etc. The control information transmittedthrough the PDCCH as described above is referred as downlink controlinformation (DCI).

Hereinafter, a downlink reference signal will be described in detail.

In the 3GPP LTE system, two kinds of DL reference signals, i.e., acommon reference signal (RS) or cell-specific RS (CRS) and a dedicatedRS or UE-specific RS (DRS) are defined so as to provide a unicastservice.

The common RS is a reference signal shared by all UEs in a cell, and isused to obtain information on a channel state and perform handovermeasurement. The dedicated RS is a reference signal for only a specificUE, and is used to perform data demodulation. The CRS is a cell-specificreference signal, and DRS is a UE-specific reference signal.

The UE measures a common RS and informs the BS of feedback informationsuch as channel quality information (CQI), preceding matrix indicator(PMI) and rank indicator (RI). The BS performs DL frequency domainscheduling using the feedback information received from the UE.

To transmit an RS to the UE, the BS allocates a resource inconsideration of the amount of radio resource to be allocated to the RS,the exclusive position of the RS and the dedicated RS, the position of asynchronization channel (SCH) and a broadcast channel (BCH), the densityof the dedicated RS, etc.

If a relatively large quantity of resource is allocated for the RS, itis possible to obtain a high channel estimation performance, but a datatransmission rate is decreased. If a relatively small quantity ofresource is allocated for the RS, it is possible to obtain a high datatransmission rate, but the channel estimation performance may bedegraded due to a low density of the RS.

Meanwhile, in the 3GPP LTE system, the DRS is used only for datademodulation, and the CRS are used for both objects of channelinformation acquisition and data demodulation. Particularly, the CRS istransmitted every subframe in a broad band, and is transmitted for eachantenna port of the BS. For example, when the number of transmitantennas of the BS is two, CRSs for antenna ports 0 and 1 aretransmitted. When the number of transmit antennas of the BS is four,CRSs for antenna ports 0 to 3 are transmitted.

FIG. 5 illustrates an example of the structure of the uplink subframe inthe 3GPP LTE.

Referring to FIG. 5, the uplink subframe may be divided into a controlregion in which a physical uplink control channel (PUCCH) carryinguplink control information is allocated and a data region in which aphysical uplink shared channel (PUSCH) carrying uplink data informationis allocated. To maintain a single carrier property, RSs allocated toone UE are contiguous in the frequency domain. The one UE cannottransmit the PUCCH and the PUSCH at the same time.

The PUCCH for one UE is allocated as an RB pair in a subframe. RBsconstituting the RB pair occupy different subcarriers in first andsecond slots, respectively. The frequency occupied by each of the RBsconstituting the RB pair is changed at a boundary between the slots. TheUE transmits uplink control information through different subcarriersaccording to time, thereby obtaining a frequency diversity gain.

The uplink control information transmitted on the PUCCH includes hybridautomatic repeat request (HARQ) acknowledgement (ACK)/negativeacknowledgement (NACK), channel quality indicator indicating a downlinkchannel state, scheduling request (SR) that is an uplink radio resourceallocation request, etc.

The PUSCH is mapped to the UL-SCH that is a transport channel. Uplinkdata transmitted on the PUSCH may be a transport block that is a datablock for the UL-SCH transmitted for the TTI. The transport block may beuser information, or the uplink data may be multiplexed data. Themultiplexed data may be data obtained by multiplexing the transportblock for the UL-SCH and control information. For example, the controlinformation multiplexed by the data may include CQI, PMI, HARQ ACK/NACK,RI, etc. The uplink data may be composed of only the controlinformation.

Meanwhile, a high data transmission rate is required, and the most basicand stable plan for solving the high data transmission rate is toincrease a bandwidth.

However, frequency resources are currently in a saturation state,various technologies are partially used in a wide frequency band. Forthis reason, carrier aggregation (CA) has been introduced as a plan forsecuring a wideband bandwidth in order to satisfy the requirement of thehigh data transmission rate. Here, the CA is a concept of designing tosatisfy basic requirements that an independence system is operable ineach of the scattered bands and binding a plurality of bands using onesystem. In the CA, the band in which the independent system is operableis defined as a component carrier (CC).

The CA is employed not only in an LTE system but also in an LTE-advanced(hereinafter, referred to as an ‘LTE-A’).

Carrier Aggregation

A carrier aggregation system refers to a system that forms a wide bandby aggregating one or more carriers having a bandwidth narrower than adesired wideband when a radio communication system intends to supportthe wideband. The carrier aggregation system may be called as otherterms including a multiple carrier system, a bandwidth aggregationsystem, etc. The carrier aggregation system may be divided into acontiguous carrier aggregation system in which carriers are contiguousand a non-contiguous carrier aggregation system in which carriers areseparated from one another. Hereinafter, when the carrier aggregationsystem is simply called as a multiple carrier system or carrieraggregation system, it should be understood that the carrier aggregationsystem includes both cases in which component carriers are contiguousand in which component carriers are non-contiguous.

In the contiguous carrier aggregation system, a guard band may existbetween carriers. When one or more carriers are aggregated, the carriersto be aggregated may use the bandwidth used in a conventional system asit is for the purpose of backward compatibility with the conventionalsystem. For example, the 3GPP LTE system supports bandwidths of 1.4 MHz,3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz. Alternatively, the 3GPP LTEdoes not use the bandwidth used in the conventional system as it is butmay form a wideband by defining a new bandwidth.

In the carrier aggregation system, the UE may simultaneously transmit orreceive one or a plurality of carriers according to its capacity.

FIG. 6 illustrates an example of performing communication under a singlecomponent carrier situation. FIG. 6 may correspond to an example ofperforming communication in an LTE system.

Referring to FIG. 6, a general frequency division duplex (FDD) radiocommunication system transmits/receives data through one downlink bandand one uplink band corresponding thereto. The BS and the UEtransmits/receive data and/or control information scheduled as asubframe unit. The data is transmitted/received through the data regionconfigured in the uplink/downlink subframe, and the control informationis transmitted/received through the control region configured in theuplink/downlink subframe. To this end, the uplink/downlink subframecarries signals through various physical channels. Although the FDDradio communication system has been mainly described in FIG. 6, theaforementioned description may be applied to a time division duplex(TDD) radio communication system by dividing a radio frame intouplink/downlink radio frames in the time domain.

FIG. 7 illustrates an example of performing communication under amultiple component carrier situation. FIG. 7 may correspond to anexample of performing communication in an LET-A system.

The LTE-A system uses a carrier aggregation, bandwidth aggregation orspectrum aggregation using a wider uplink/downlink bandwidth byaggregating a plurality of uplink/downlink frequency blocks so as to usea wider frequency band. Each of the frequency blocks is transmittedusing a component carrier (CC). In this specification, the CC may mean afrequency block for carrier aggregation or a central carrier of thefrequency block according to the context, and the frequency block andthe central carrier are used together.

On the other hand, the 3GPP LTE system supports a case in which theuplink/downlink bandwidths are configured differently, but supports oneCC in each of the uplink/downlink bandwidths. The 3GPP LTE systemsupports a maximum bandwidth of 20 MHz, and supports only one CC in eachof the uplink/downlink bandwidths. Here, the uplink/downlink bandwidthsmay be different from each other.

However, the spectrum aggregation (bandwidth aggregation or carrieraggregation) supports a plurality of CCs. For example, if five CCs areallocated as the granularity of a carrier unit having a bandwidth of 20MHz, the spectrum aggregation can support a maximum bandwidth of 100MHz.

A pair of DL CC or UL CC and DL CC may correspond to one cell. The onecell basically includes one DL CC and optionally includes UL CC.Therefore, it may be considered that the UE communicating with the BSthrough a plurality of DL CCs receive services from a plurality ofserving cells. The DL is composed of a plurality of DL CCs, but the ULmay use only one CC. In this case, it may be considered that the UEreceives services from a plurality of serving cells in the DL andreceives a service from one serving cell in the UL.

In this meaning, the serving cell may be divided into a primary cell anda secondary cell. The primary cell operates at a primary frequency, andis used to perform an initial connection establishment process,connection re-establishment process or handover process of the UE. Theprimary cell is also referred to as a reference cell. The secondary celloperates at a secondary frequency, and may be configured after RRCconnection is established. The secondary cell may be used to provide anadditional radio resource. At least one primary cell is alwaysconfigured, and the secondary cell may be added/modified/cancelled byupper layer signaling (e.g., an RRC message).

Referring to FIG. 7, five CCs having a bandwidth of 20 MHz may beaggregated in each of the UL/DL, thereby supporting a bandwidth of 100MHz. CCs may be adjacent or non-adjacent to one another in the frequencydomain. For convenience, FIG. 9 illustrates a case in which thebandwidths of UL and DL CCs are identical and symmetric to each other.However, the bandwidth of each of the CCs may be independentlydetermined. For example, the bandwidth of the UL CC may be configured as5 MHz(UL CC0)+20 MHz(UL CC1)+20 MHz(UL CC2)+20 MHz(UL CC3)+5 MHz(ULCC4). Asymmetric carrier aggregation may be implemented in which thenumber of UL CCs is different from that of DL CCs. The asymmetriccarrier aggregation may be formed due to limitation of an availablefrequency band or may be artificially formed by network configuration.For example, although the frequency band of the entire system iscomposed of N CCs, the frequency band received by a specific UE may belimited to M(<N) CCs. Various parameters for the CA may be configured ina cell-specific, UE group-specific or UE-specific manner.

Although it has been illustrated in FIG. 7 that the UL and DL signalsare respectively transmitted through CCs mapped one by one, the CCthrough which a signal is substantially transmitted may be changeddepending on the network configuration or kind of signal.

For example, when a scheduling command is downlink-transmitted throughthe DL CC1, data according to the scheduling data may be transmittedthrough another DL CC or UL CC. Control information related on the DL CCmay be uplink-transmitted through a specific UL CC regardless of thepresence of mapping. Similarly, DL control information may also betransmitted through a specific DL CC.

FIG. 8 is a block diagram illustrating a single carrier-frequencydivision multiple access (SC-FDMA) transmission scheme that is an uplinkaccess scheme employed in the 3GPP LTE.

SC-FDMA is employed in the uplink of LTE. Here, the SC-FDMA is a schemesimilar to OFDM, but can reduce power consumption of a portable terminaland cost of a power amplifier by decreasing a peak to average powerratio (PAPR).

The SC-FDMA is a scheme similar to the OFDM in which a signal is dividedinto sub-bands to be transmitted through sub-carriers using fast Fouriertransform (FFT) and inverse-FFT (IFFT). The SC-FDMA is identical to theconventional OFDM scheme in that a guard interval (cyclic prefix) isused so that it is possible to utilize a simple equalizer in thefrequency domain with respect to inter-symbol interference (ISI).However, the power efficiency of a transmitter has been improved bydecreasing the PAPR at a transmitter terminal by about 2 to 3 dB usingan additional unique technique.

That is, the problem of the conventional OFDM receiver is that signalscarried by each sub-carrier on a frequency axis are converted intosignals on a time axis by the IFFT. Since parallel equal operations areperformed in the IFFT, an increase in the PAPR occurs.

Referring to FIG. 8, to solve such a problem, a discrete Fouriertransform (DFT) 12 is first performed on information before a signal ismapped to a sub-carrier in the SC-FDMA. Sub-carrier mapping 13 isperformed on a signal spread (or precoded in the same meaning) by theDFT, and the signal subjected to the sub-carrier mapping is convertedinto a signal in the time axis by performing an IFFT 14.

In this case, unlike the OFDM, the PAPR of a signal in the time domainafter the IFFT 14 is not increased so much by the correlation among theDEF 12, the sub-carrier mapping 13 and the IFFT 14, and thus the SC-FDMAis advantageous in terms of transmission power efficiency.

That is, a transmission scheme in which the IFFT is performed after DFTspreading is referred to as the SC-FDMA.

As such, the SC-FDMA has a similar structure to the OFDM, therebyobtaining the signal strength for a multi-path channel, and the SC-FDMAcompletely prevents the PAPR from being increased through the throughthe IFFT in the conventional OFDM, thereby enabling the use of a poweramplifier. Meanwhile, the SC-FDMA may also be called as DEF spread OFDM(DEF-s-OFDM).

That is, the PAPR or cubic metric (CM) may be decreased in the SC-FDMA.When the SC-FDMA transmission scheme is used, it is possible to avoid anon-linear distortion period of the power amplifier, and thus thetransmission power efficiency can be improved in an UE of which powerconsumption is limited. Accordingly, it is possible to increase a userthroughput.

Meanwhile, the standardization of the LTE-A more improved than the LTEhas been actively performed in the 3GPP. In the process of standardizingthe LTE-A, the SC-FDMA-based scheme and the OFDM scheme competed witheach other, but a clustered DEF-s-OFDM scheme that allows non-contiguousresource allocation has been employed.

Hereinafter, the LTE-A system will be described in detail.

FIG. 9 is a block diagram a clustered discrete Fouriertransform-spread-orthogonal frequency division multiplexing (DFT-s-OFDM)transmission method employed as an uplink access method in theLTE-advanced standard.

The important feature of the clustered DFT-s-OFDM is that it is possibleto flexibly cope with a frequency selective fading environment byenabling frequency selective resource allocation.

In the clustered DFT-s-OFDM scheme employed as the uplink access schemeof the LTE-A, the non-contiguous resource allocation is alloweddifferently from the SC-FDMA that is an uplink access scheme of theconventional LTE, and thus transmitted uplink data can be divided intoseveral cluster units.

That is, the LTE system maintains a single carrier characteristic in theUL. On the other hand, the LTE-A allows a case in which data subjectedto DFT-precoding is non-contiguously allocated on the frequency axis orthe PUSCH and PUCCH are transmitted at the same time.

SUMMARY OF THE INVENTION

Therefore, an aspect of the detailed description is to provide a methodof performing cell measurement and a method of providing information forcell measurement, which enable a UE to effectively measure referencesignal received power (RSRP) and reference signal received quality(RSRQ).

Another aspect of the detailed description is to provide a methodcapable of efficiently measuring RSRP and RSRQ of serving andneighboring cells in an environment in which base stations of differentnetworks coexist in an LTE-based radio communication system.

Still another aspect of the detailed description is to provide a methodcapable of efficiently measuring RSRP and RSRQ of serving andneighboring cells when enhanced inter-cell interference coordination(eICIC) is driven in an LTE-A system currently discussed in the 3GPP.

To achieve these and other advantages and in accordance with the purposeof this specification, as embodied and broadly described herein, thereis provided a method of providing information for cell measurement, themethod including: configuring a subframe for performing measurement withrespect to a first cell, wherein the configured subframe is differentfrom a subframe for performing measurement with respect to a secondcell; and transmitting, from the first cell to a user equipment (UE), afirst pattern information on the configured subframe and a secondpattern information indicating the subframe for performing measurementwith respect to the second cell, wherein the first or second patterninformation indicates the subframe for measurement as a bit ‘1,’ and thefirst or second pattern information indicates at least one subframe aper radio frame, used for performing the measurement.

The first or second pattern information may be represented as a bitstream, and a first bit of the bit stream may correspond to a zerothsubframe of a frame satisfying SFN mod x=0. Here, the x denotes a sizeobtained by dividing 10 into the bit stream, and the SFN denotes asystem frame number.

The first or second pattern information may be a time domain measurementresource restriction pattern or measSubframePattern.

The first pattern information may be measSubframePattern-Serv, or thesecond pattern information may be measSubframePattern-Neigh.

The configured subframe may be configured in consideration of a generalalmost black subframe (ABS) or MBMS single frequency network (MBSFN) ABSother than an MBSFN.

The second pattern information is received through X2 interface-basedsignaling.

In the transmitting of the first and second pattern information, thefirst pattern information may be transmitted through a radio resourcecontrol (RRC) message.

The RRC message is an RRC connection reconfiguration message.

To achieve the above aspect of this specification, there is provided amethod of performing measurement in a UE placed within a coverage of aserving cell and a coverage of a neighboring cell, the method including:obtaining pattern information on a subframe for performing measurement,wherein the pattern information of the serving cell is configureddifferently from that of the neighboring cell; and performingmeasurement on the serving cell and the neighboring cell on differentsubframes according to the pattern information, wherein the patterninformation indicates the subframe for measurement as a bit ‘1,’ and thepattern information indicates at least one subframe per radio frame,used for performing the measurement.

The pattern information may be represented as a bit stream, and a firstbit of the bit stream may correspond to a zeroth subframe of a framesatisfying SFN mod=0. Here, the x denotes a size obtained by dividing 10into the bit stream, and the SFN denotes a system frame number.

The pattern information may be a time domain measurement resourcerestriction pattern or measSubframePattern.

The pattern information may include a first pattern information on theserving cell and a second pattern information on the neighboring cell.The first pattern information may be measSubframePattern-Neigh, or thesecond pattern information may be measSubframePattern-Serv

The subframe may be configured as a general ABS or MBSFN ABS other thanan MBSFN.

The performing of the measurement may include measuring one or more ofreference signal received power (RSRP) and reference signal receivedquality (RSRQ) through a cell-specific reference signal (CRS).

To achieve the above aspect of this specification, there is provided abase station including: a controller configured to configure a subframefor performing measurement, wherein the configured subframe is differentfrom a subframe for performing measurement on a neighboring cell; and atransmitter configured to transmit a first pattern information on theconfigured subframe and a second pattern information indicating thesubframe for performing the measurement with respect to the neighboringcell to a UE, wherein the first or second pattern information indicatesthe subframe for measurement as a bit ‘1,’ and the first or secondpattern information indicates at least one subframe per radio frame,used for performing the measurement.

To achieve the above aspect of this specification, there is provided aUE including: a receiver configured to obtain pattern information on asubframe for performing measurement from a serving cell; and acontroller configured to perform measurement with respect to the servingcell and a neighboring cell on different subframes according to thepattern information, when a user equipment is placed within a coverageof the serving cell and a coverage of the neighboring cell, wherein thepattern information indicates the subframe for measurement as a bit ‘1,’and the pattern information indicates at least one subframe per radioframe, used for performing the measurement.

Further scope of applicability of the present application will becomemore apparent from the detailed description given hereinafter. However,it should be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 illustrates a radio communication system;

FIG. 2 illustrates a structure of a radio frame in 3rd generationpartnership project long term evolution (3GPP LTE);

FIG. 3 is an exemplary view illustrating a resource grid for one uplinkslot in the 3GPP LTE;

FIG. 4 illustrates a structure of a downlink subframe;

FIG. 5 illustrates an example of the structure of the uplink subframe inthe 3GPP LTE;

FIG. 6 illustrates an example of performing communication under a singlecomponent carrier situation;

FIG. 7 illustrates an example of performing communication under amultiple component carrier situation;

FIG. 8 is a block diagram illustrating a single carrier-frequencydivision multiple access (SC-FDMA) transmission scheme that is an uplinkaccess scheme employed in the 3GPP LTE;

FIG. 9 is a block diagram a clustered discrete Fouriertransform-spread-orthogonal frequency division multiplexing (DFT-s-OFDM)transmission method employed as an uplink access method in theLTE-advanced standard;

FIG. 10 is a structural diagram of an evolved mobile communicationnetwork;

FIG. 11 illustrates a case in which pico and femto cells coexist withina coverage of a macro cell;

FIG. 12 illustrates a system for implementing a multimediabroadcast/multicast service (MBMS);

FIG. 13 is an exemplary diagram illustrating enhanced inter-cellinterference coordination (eICIC) for solving inter-base stationinterference;

FIG. 14A to 14D are exemplary diagrams illustrating subframes operatingas almost blank subframes (ABSs);

FIG. 15 illustrates a process of measuring reference signal receivedpower (RSRP) and reference signal received quality (RSRQ) through acell-specific RS (CRS);

FIG. 16 illustrates a process of providing a user equipment (UE) withinformation for cell measurement;

FIG. 17 illustrates control plane and user plane architectures of aradio interface protocol between an UE and an evolved-universalterrestrial radio access network (E-UTRAN) based on a 3GPP radio accessnetwork standard;

FIG. 18 illustrates messages transmitted/received based on thearchitecture of the protocol shown in FIG. 17;

FIG. 19 illustrates an example of a time domain measurement resourcerestriction pattern;

FIG. 20 is an exemplary diagram illustrating a process of measuring RSRPand RSRQ;

FIG. 21 is an exemplary diagram illustrating a situation in which a UEexists within a coverage of a pico cell and a coverage of a macro cell(eNodeB);

FIG. 22 illustrates an example in which subframes for cell measurementare differently configured under a situation in which a macro cell andpico/femto cells coexist;

FIG. 23 illustrates another example in which the subframes for cellmeasurement are configured differently in the situation in which themacro cell and the pico/femto cells coexist; and

FIG. 24 is a configuration block diagram illustrating a UE and a basestation (BS) according to an exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The following technology may be used in various multiple access schemessuch as code division multiple access (CDMA), frequency divisionmultiple access (FDMA), time division multiple access (TDMA), orthogonalfrequency division multiple access (OFDMA) and single carrier-frequencydivision multiple access (SC-FDMA). The CDMA may be implemented by aradio technology such as universal terrestrial radio access (UTRA) orCDMA2000. The TDMA may be implemented by a radio technology such as aglobal system for mobile communications (GSM)/general packet radioservice (GPRS)/enhanced data rates for GSM evolution (EDGE). The OFDMAmay be implemented by a radio technology such as institute of electricaland electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802.20 or evolved UTRA (E-UTRA). The UTRA is a portion of auniversal mobile telecommunications system (UMTS). 3rd generationpartnership project (3GPP) long term evolution (LTE) is a portion of anevolved UMTS (E-UMTS) using the E-UTRA, which employs the OFDMA indownlink and the SC-FDMA in uplink. LTE-advanced (LTE-A) is an evolutionof the 3GPP LTE.

Technical terms used in this specification are used to merely illustratespecific embodiments, and should be understood that they are notintended to limit the present disclosure. As far as not being defineddifferently, all terms used herein including technical or scientificterms may have the same meaning as those generally understood by anordinary person skilled in the art to which the present disclosurebelongs to, and should not be construed in an excessively comprehensivemeaning or an excessively restricted meaning. In addition, if atechnical term used in the description of the present disclosure is anerroneous term that fails to clearly express the idea of the presentdisclosure, it should be replaced by a technical term that can beproperly understood by the skilled person in the art. In addition,general terms used in the description of the present disclosure shouldbe construed according to definitions in dictionaries or according toits front or rear context and should not be construed to have anexcessively restrained meaning.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Itwill be further understood that the terms “includes” and/or “including,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence and/or addition of one or more otherfeatures, integers, steps, operations, elements, components, and/orgroups thereof.

In the following description, suffixes “module” and “unit or portion”for components used herein in description are merely provided only forfacilitation of preparing this specification, and thus they are notgranted a specific meaning or function.

It will be understood that, although the terms “first,” “second,” etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another element. Thus, a “first” element discussedbelow could also be termed as a “second” element without departing fromthe teachings of the present invention.

In the drawings, the thickness of layers, films and regions areexaggerated for clarity. Like numerals refer to like elementsthroughout.

Description will now be given in detail of the exemplary embodiments,with reference to the accompanying drawings. For the sake of briefdescription with reference to the drawings, the same or equivalentcomponents will be provided with the same reference numbers, anddescription thereof will not be repeated. It will also be apparent tothose skilled in the art that various modifications and variations canbe made in the present invention without departing from the spirit orscope of the invention. Thus, it is intended that the present inventioncover modifications and variations of this invention provided they comewithin the scope of the appended claims and their equivalents.

Hereinafter, although a user equipment (UE) is shown in the drawings,the UE may be called as a terminal, mobile equipment (ME), a mobilestation (MS), user terminal (UT), subscriber station (SS), wirelessdevice, handheld device or access terminal (AT). The UE may be aportable device having a communication function, such as a cellularphone, personal digital assistant (PDA), smart phone, wireless modem ornotebook computer, or may be a device that cannot be carried, such as apersonal computer (PC) or vehicle mounting device.

FIG. 10 is a structural diagram of an evolved mobile communicationnetwork.

One of the important characteristics in the structure of the network ofFIG. 10 is that it is based on a 2 tier model an eNodeB 220 of theevolved UTRAN and a gateway (GW) of the core network. The eNodeB 220 hasa similar function, although not exactly the same, to an eNodeB 210 andRNC of the existing UMTS system, and the gateway has a function similarto the SGSN/GGSN of the existing system.

Another important characteristic is that different interfaces areexchanged by the control plane and the user plane between the accessnetwork and the core network. While an Iu interface exists between theRNC and SGSN in the existing UMTS system, a mobile management entity(MME) 510 handling the processing of a control signal has a structureseparated from the GW, and therefore, two separate interfaces, i.e.,S1-MME and S1-U, are used. The GW includes a serving-gateway(hereinafter, referred to as an S-GW 520) and a packet data networkgateway (hereinafter, referred to as a PDN-GW or P-GW 530).

Meanwhile, in the 3rd or 4th generation mobile communication system,attempts to increase the capacity of a cell are continuously made tosupport high-capacity and bidirectional services including streaming,etc.

That is, as various large-capacity transmission technologies arerequired together with the development of communications and the spreadof multimedia technologies, a method of allocating a larger number offrequency resources may be used as a method of increasing radiocapacity. However, since the number of frequency resources is limited,there is a limitation when the larger number of frequency resources areallocated to a plurality of users.

Approaches for using a high frequency band and decreasing the radius ofa cell have been made to increase the capacity of the cell. A pico orfemto cell applied to a cell having a small radius can use a higherfrequency band than the frequency used in the existing cellular system,and thus it is possible to transmit a larger amount of information.However, since a larger number of base stations (BSs) are installed inthe same area, installation cost is increased.

An approach for using a femto/pico cell has been proposed among theapproaches for increasing the capacity of the cell having the smallradius. The pico cell refers to a small-sized cell having a radiussmaller than that of a macro cell, and the femto cell refers to a cellmanaged by a home eNodeB (HeNB). Since the pico cell is installed by aprovider and the femto cell is installed by a user, it is assumed thatthe provider does not exactly recognize the existence of the femto cellin the 3GPP.

In the 3GPP, studies on the femto/pico cell 300 have been mainlyconducted by RAN WG3 under the name of home (e)NodeB. In this case, theeNodeB 220 or NodeB 210 is relatively referred to as a macro cell.Hereinafter, when the NodeB 210 or eNodeB 220 are referred to as a macrocell, reference numeral 200 is used.

In this specification, descriptions will be given based on terminologiesof the 3GPP, and the (e)NodeB is used when the NodeB or eNodeB ismentioned together with the (e)NodeB.

Interfaces shown by a dotted line are used for transmission of a controlsignal between the femto/pico cell 300 and the MME 510. Interfaces shownby a solid line are used for transmission of data on a user plane.

FIG. 11 illustrates a case in which pico and femto cells coexist withina coverage of a macro cell.

As shown in FIG. 11, when different kinds of networks including thepico/femto cells, etc. coexist within the coverage of a macro cell, theinterference between the networks is problematic.

That is, the pico or femto cell is placed in the macro cell, and in thissituation, an UE place at the boundary between the overlapped cells isinfluenced by interference between signals transmitted from therespective cells.

As a specific example, when a UE 100 connected to the pico cell 200 isplaced at a boundary of the pico cell 300, the connection between the UE100 and the pico cell 300 may be stopped due to the interference fromthe macro cell 200. This means that the coverage of the pico cell 300 isnarrower than the expectation of the provider.

As another example, when the UE 100 connected to the macro cell 200 isplaced in the area of the femto cell 300, the connection between the UE100 and the macro cell 200 may be stopped due to the interference fromthe femto cell 300. This means that a shadow region in the macro cell200 has occurred.

The first example is called as a macro-pico problem and the secondexample is called as a macro-femto problem. These problems have comeinto the limelight as important problems to be solved in the differentkinds of networks.

The most basic method for solving such an interference problem is thatdifferent frequencies are used between the different kinds of networks.However, since the frequencies are scarce and expensive resources, thesolution through frequency division was not welcomed by the provider.

Therefore, attempts to solve the inter-cell interference problem havebeen made through time division in the 3GPP.

Accordingly, studies on enhanced inter-cell interference coordination(eICIC) have recently been actively conducted as one of interferencecoordination methods in the 3GPP.

The time division method introduced in LTE Release-10 is called as theeICIC meaning that the time division method has been evolved as comparedwith the existing frequency division method. Here, a cell causinginterference is defined as an aggressor cell or primary cell, and a cellreceiving interference is defined as a victim cell or secondary cell.The time division method is a method is a method in which the aggressorcell or primary cell stops data transmission in a specific subframe, soas to enable the UE to maintain connection to the victim cell orsecondary cell in the corresponding subframe. That is, in the timedivision method, when the macro cell and pico cell or the macro cell andfemto cell coexist, one BS temporarily stops the transmission of asignal to the UE receiving a considerably high interference in any area,so that an interference signal is hardly transmitted to the UE.

In the macro-pico or macro-femto problem described above, the macro cellmay be the aggressor cell or primary cell, and the pico cell may be thevictim cell or secondary cell. On the contrary, the pico cell may be theaggressor cell or primary cell, and the macro cell may be the victimcell or secondary cell.

Meanwhile, the specific subframe in which the data transmission isstopped is referred to as an almost blank subframe (ABS), and any dataexcept essentially required control information is not transmitted in asubframe according to the ABS. The essentially required controlinformation is, for example, a cell-specific reference signal (CRS). Inthe current 3GPP LTE/LTE-A standard, the CRS exists on zeroth, fourth,seventh and eleventh OFDM symbols in each subframe on the time axis.

In a next-generation mobile communication system, a multimediabroadcast/multicast service has been proposed for the purpose ofbroadcasting services.

FIG. 12 illustrates a system for implementing a multimediabroadcast/multicast service (MBMS).

As can be seen with reference to FIG. 12, the system for implementingthe MBMS includes an MBMS GW 560, an MB-SC 570, a content provider 580and an MCE 590, in addition to the eNodeB 220 and the MME 510.

Meanwhile, an MBMS single frequency network (MBSFN) in which a pluralityof eNodeBs 220 transmit the same data at the same time is applied in oneservice area.

The MBMS refers to a service that provides a streaming service,background broadcast service or multicast service to a plurality of UEsusing a downlink-dedicated MBMS bearer service. In this case, the MBMSmay be divided into a multi-cell service in which the same service isprovided to a plurality of cells and a single cell service in which oneservice is provided to only one cell.

When the UE receives the multi-cell service, the UE may receive themulti-cell service by combining the same service transmitted fromseveral cells through the MBSFN scheme.

Meanwhile, the subframe through which the MBMS is transmitted issignaled to an MBSFN subframe, so that the UE can recognize thetransmitted MBMS.

FIG. 13 is an exemplary diagram illustrating enhanced inter-cellinterference coordination (eICIC) for solving inter-base stationinterference.

As can be seen with reference to FIG. 13(a), the macro cell, i.e., theeNodeB 220, and the pico cell 300 exchange information on the MBSFNsubframe with each other through an X2 interface.

For example, the macro cell, i.e., the eNodeB 220 allows the informationon the MBSFN subframe and information on a subframe operating as the ABSto be included in an MBSFN subframe info IE, and transmits the MBSFNsubframe info IE through an X2 interface-based request message.

Meanwhile, the pico cell 300 also allows the information on the MBSFNsubframe and the information on the subframe operating as the ABS to beincluded in the MBSFN subframe info IE, and transmits the MBSFN subframeinfo IE through the X2 interface-based request message.

As such, the macro cell, i.e., the eNodeB 220, and the pico cell 300 canexchange the information on the MBSFN subframe with each other throughthe X2 interface.

However, the macro cell, i.e., the eNodeB 220, and the femto cell 300have no X2 interface. To obtain information on the MBSFN of the macrocell, i.e., the eNodeB 220, the femto cell 300 may obtain systeminformation broadcasted by wireless from the macro cell, i.e., theeNodeB 220, thereby obtaining the information on the MBSFN subframe.Alternatively, the femto cell 300 may obtain the information on theMBSFN subframe of the macro cell, i.e., the eNodeB 200 from a controlstation of the core network.

Alternatively, if the information on the MBSFN subframe of the macrocell, i.e., the eNodeB 220 is determined, the information on the MBSFNsubframe may be applied to the femto cell 300 through operations andmanagement (OAM).

Referring to FIG. 13(b), a subframe configured as the MBSFN by the picocell 300 is shown. The pico cell 300 configures the correspondingsubframe as the MBSFN and informs the macro cell, i.e., the eNodeB 220of the corresponding subframe through the X2 interface. Then, the macrocell, i.e., the eNodeB 220 operates the corresponding subframe as theABS.

The pico cell 300 performs data transmission in the data region of thecorresponding subframe, and the CRS is transmitted on zeroth, fourth,seventh and eleventh symbols.

On the other hand, if the eICIC is applied to the macro cell, i.e., theeNodeB 220, the macro cell, i.e., the eNodeB 220 does not any data inthe data region of the corresponding subframe, thereby preventinginterference. However, the macro cell, i.e., the eNodeB 220 transmitsonly the CRS of the corresponding subframe.

The UE measures reference signal received power (RSRP) and referencesignal received quality (RSRQ) using CRSs respectively received from themacro cell, i.e., the eNodeB 220, and the pico cell 300. As a specificexample, when a serving cell of the UE 100 corresponds to macro cell andthe pico cell 300 corresponds to a neighboring cell, the UE 100 measuresthe RSRP and RSRQ of the serving cell through the CRS from the macrocell, i.e., the eNodeB 220, and measures the RSRP and RSRQ of theneighboring cell through the CRS from the pico cell 300.

In the current 3GPP LTE/LET-A standard, the CRS exists on the zeroth,fourth, seventh and eleventh OFDM symbols in each subframe on the timeaxis. For the purpose of compatibility with an LTE UE, the eICIC of theLTE-A does not applies a separate subframe but uses an ABS in which dataof the other portions except a minimum signal necessary for theoperation of the UE, including the CRS, is not allocated. In the MBSFNABS subframe, the other CRSs except the first CRS are additionallyremoved, so that the interference between the CRSs can be excluded infourth, seventh and eleventh OFDM symbol periods including the otherCRSs except the first CRS.

FIG. 14A to 14D are exemplary diagrams illustrating subframes operatingas ABSs.

Referring to FIG. 14A, a relation between macro and pico cells in asubframe operating as a non-MBSFN, i.e., a general subframe is shown.The macro cell transmits data in a data region of the correspondingsubframe, and transmits CRSs through zeroth, fourth, seventh andeleventh symbols. If the macro cell transmits the CRS through the samesymbol, the CRSs collide with each other, and therefore, theinterference between the CRSs occurs.

Referring to FIG. 14B, a relation between macro and pico cells in asubframe operating as a non-MBSFN, i.e., a general subframe is shown.The macro cell transmits data in a data region of the correspondingsubframe, and transmits CRSs through zeroth, fourth, seventh andeleventh symbols. If the macro cell transmits the CRSs through thezeroth, fourth, seventh and eleventh symbols using different resources,it is possible to avoid the collision between the CRSs.

Referring to FIG. 14C, a relation between macro and pico cells on asubframe configured as an MBSFN by the pico cell 300. The pico cell 300transmits data in a data region of the subframe configured as the MBSFN.The pico cell 300 transmits CRSs through zeroth, fourth, seventh andeleventh symbols in the control region of the subframe. On the otherhand, if the eICIC is applied to the macro cell 220, the macro cell 220does not transmit the data in the data region. However, the macro cell220 CRSs through the zeroth symbol on the subframe. That is, in an MBSFNABS subframe, the other CRSs except the first CRS are additionallyremoved, so that the interference between the CRSs can be excluded infourth, seventh and eleventh OFDM symbol periods including the otherCRSs except the first CRS. Accordingly, only the CRSs transmittedthrough the zeroth symbol collide with each other, and therefore, theinterference between the CRSs occurs.

Referring to FIG. 14D, a relation between macro and pico cells on asubframe configured as an MBSFN by the pico cell 300. The pico cell 300transmits data in a data region of the subframe configured as the MBSFN.The pico cell 300 transmits CRSs through zeroth, fourth, seventh andeleventh symbols in the control region of the subframe. On the otherhand, if the eICIC is applied to the macro cell 220, the macro cell 220does not transmit the data in the data region. However, the macro cell220 CRSs through the zeroth symbol on the subframe. If the pico cell 300transmits the CRSs through the zeroth symbol using different resources,it is possible to avoid the collision between the CRSs.

As described above, when the UE measures RSRP/RSRQ by receiving the CRSsfrom the pico cell 300 under the situation in which the macro cell 220and the pico cell 300 coexist, FIG. 14A illustrates a case in which thepositions of the CRSs of the macro and pico cells are the same as eachother. Therefore, the overlapped CRSs act as the interference betweenthe CRSs, and accordingly, the transmission performance of a signal isremarkably lowered.

FIG. 15 illustrates a process of measuring RSRP and RSRQ through a CRS.

As can be seen with reference to FIG. 15, when the pico cell 300 is aserving cell and the macro cell, i.e., the eNodeB 220 is a neighboringcell with respect to the UE 100, the serving cell and the neighboringcell transmit CRSs, respectively. Then, the UE 100 measures the RSRP andRSRQ through the CRSs, and transmits the measured result to the picocell 300 that is the serving cell.

Hereinafter, the serving cell transmits necessary information to the UEso as to perform measurement will be described.

FIG. 16 illustrates a process of providing a UE with information forcell measurement. FIG. 17 illustrates control plane and user planearchitectures of a radio interface protocol between an UE and anevolved-universal terrestrial radio access network (E-UTRAN) based on a3GPP radio access network standard. FIG. 18 illustrates messagestransmitted/received based on the architecture of the protocol shown inFIG. 17.

As can be seen with reference to FIG. 16(a), the UE 100 establishes anRRC connection procedure with the pico/femto cell 300 that is a servingcell.

Before describing RRC, the architecture of the protocol among the UE100, the serving cell 220 or 300 and the MME 510 will be described withreference to FIG. 17.

The protocol among the UE 100, the serving cell 220 or 300 and the MME510 may be divided into a control plane and a user plane. The controlplane means a gateway through which control messages used for the UE andnetwork to manage a call are transmitted. The user plane means a gatewaythrough which data generated in an application layer, e.g., voice data,Internet packet data, etc. is transmitted.

A physical layer as a first layer provides an information transferservice to an upper layer using a physical channel. The physical layeris connected to a medium access (MAC) control layer above the physicallayer via a transport channel. Data is transferred between the MAC layerand the physical layer via the transport channel. Data are transferredbetween one physical layer of a transmitting side and the other physicallayer of a receiving side via the physical channel. The physical channeluses time and frequency as radio resources. Specifically, the physicalchannel is modulated using an orthogonal frequency division multipleaccess (OFDMA) scheme in a downlink, and is modulated using a singlecarrier frequency division multiple access (SC-FDMA) scheme in anuplink.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer above the MAC layer via a logical channel. The RLClayer of the second layer supports reliable data transfer. The RLC layermay be implemented as a functional block inside the MAC layer. Toeffectively transmit IP packets such as IPv4 or IPv6 within a radiointerface having a narrow bandwidth, a packet data convergence protocol(PDCP) layer of the second layer performs header compression to reducethe size of unnecessary control information.

A radio resource control (RRC) layer located on a lowest portion of athird layer is defined in only the control plane. The RRC layer isassociated with configuration, re-configuration and release of radiobearers RBs) to be in charge of controlling the logical, transport andphysical channels. The RB means a service provided by the second layerfor the data transfer between the UE and the network. To this end, theRRC layers of the UE and the network exchange RRC messages with eachother. If the RRC layer of the UE is RRC connected to the RRC layer ofthe network, the UE is in RRC connected mode. If not so, the UE is inRRC idle mode. A non-access stratum (NAS) layer located above the RRClayer performs functions such as session management and mobilitymanagement.

Meanwhile, as can be seen with reference to FIG. 18, the messagestransmitted/received between the UE 100 and the serving cell, e.g., theeNodeB 220 or pico/femto cell 300 are messages based on an RRC protocol.The messages transmitted/received between the serving cell 220 or 300and the MME 510 are messages based on an S1 application protocol(S1-AP).

The messages transmitted/received between the UE 100 and the MME 510 aremessages based on a NAS protocol. The messages based on the NAS protocolare encapsulated in a message based on the RRC protocol and the S1-APmessage and then transmitted.

Hereinafter, an RRC state of a HE and an RRC connection will bedescribed.

The RRC state refers to whether or not the RRC layer is in a logicalconnection with the RRC layer of the E-UTRAN. When the RRC layers arelogically connected to each other, the RRC state is called as anRRC_CONNECTED state. When the RRC layers are not logically connected toeach other, the RRC state is called as RRC_IDLE state. Since an RRCconnection exists in the UE of the RRC_CONNECTED state, the E-UTRAN canrecognize the existence of the corresponding UE in the cell unit, andthus can effectively control the UE. On the other hand, the E-UTRANcannot recognize the UE of the RRC_IDLE state, and the core networkmanages the UE in tracking area units, which correspond to area unitslarger than the cell units. That is, the UE in the RRC_IDLE state isrecognized only in large area units, and the RRC is necessarily shiftedto the RRC_CONNECTED state in order to receive general mobilecommunication services such as sound or data.

When a user initially turns on the power of the UE, the UE searches foran adequate cell and then remains in the RRC_IDLE state within thecorresponding cell. When the UE in the RRC Idle state is required tomake an RRC connection, the RRC of the UE can make an RRC connectionwith the RRC of the E-UTRAN through an RRC connection procedure, therebyshifting to the RRC_CONNECTED state. There are various cases in whichthe UE in the RRC_IDLE state is required to make an RRC connection. Forexample, there is a case in which an uplink data transmission isrequired due to reasons such as the user's attempt to make a phone call,or a case in which a response message transmission is required to bemade after receiving a paging message from the E-UTRAN.

As such, the UE 100 performs the RRC connection procedure so as to shiftto the RRC_Connected state, i.e., the RRC connection state. As shown inFIG. 16(a), the UE 100 transmits an RRC connection request message tothe serving cell, i.e., the pico/femto cell 300.

If the UE 100 receives an RRC connection setup message from the servingcell in response to the RRC connection request message, the UE 100transmits an RRC connection setup complete message to the serving cell.

Meanwhile, when it is required to reconfigure the RRC connection aftershifting to the RRC connection state, as shown in FIG. 16(b), theserving cell, i.e., the pico/femto cell 300 transmits an RRC connectionreconfiguration message to the UE 100.

The RRC reconfiguration message may include, for example, a radioresource configuration dedicated information element (IE) and ameasurement configuration (MeasConfig). Table 1 shows informationincluded in the RRC reconfiguration message as shown in this figure.

TABLE 1 measConfig mobillityControlInfo dedicatedInfoNASListradioResourceConfigDedicated securityConfigH0 nonCriticalExtension

As such, the radio resource configuration dedicated IE, the measurementconfiguration (MeasConfig), etc. are included in the RRC reconfigurationmessage.

The radio resource configuration dedicated IE is used toconfigure/modify/cancel radio bearers, to modify MAC configuration, etc.The radio resource configuration dedicated IE includes subframe patterninformation. The subframe pattern information is information on ameasurement resource restriction pattern on the time domain, formeasuring RSRP and RSRQ of a primary cell (PCell).

The radio resource configuration dedicated IE includes fields as shownin the following table.

TABLE 2 RadioResourceConfigDedicated measSubframePatternPCell-r10

The RadioResourceConfigDedicated field includes factors as shown in thefollowing table.

TABLE 3 RadioResourceConfigDedicated field descriptionslogicalChannelConfig is used as a selection for indicating that thelogical channel configuration for SRBs( ) is clearly signaled or thatthe logical channel configuration is set to a default logical channelconfiguration for SRB1 logicalChannelIdentity is a logical channelidentifier for identifying both uplink (UL) and downlink (DL)mac-MainConfig is a selection used to indicate that the mac-MainConfigis clearly signaled or that the mac-MainConfig is set to default mainconfiguration measSubframePatternPCell is a time domain measurementresource restriction pattern for measuring RSRP and RSRQ of a primarycell (PCell, i.e., serving cell) physicalConfigDedicated is defaultdedicated physical configuration

As described above, measSubframePatternPCell or measSubframePattern-Servindicating the time domain measurement resource restriction pattern formeasuring the RSRP and RSRQ of the primary cell (PCell, i.e., servingcell) is included in the RadioResourceConfigDedicated field within theRRC reconfiguration message.

Meanwhile, the measurement configuration (MeasConfig) includes an IE asshown in the following table.

TABLE 4 MeasConfig ::= -- Measurement objects   measObjectToRemoveList  measObjectToAddMoList

The measObjectToRemoveList indicating a list of measObject to be removedand measObjectToAddModList indicating a list to be newly added ormodified are included in the measurement objects IE.

MeasObjectCDMA2000, MeasObjectEUTRA, MeasObjectGERAN, etc. are includedin the measObject according to a communication technology.

Meanwhile, the MeasObjectEUTRA IE includes information applied for thepurpose of an intra-frequency or inter-frequency for E-UTRA cellmeasurement. The MeasObjectEUTRA IE is as shown in the following table.

TABLE 5 1) MeasObjectEUTRA - neighCellConfig -measSubframePatternConfigNeigh-r10 2) MeasSubframePatternConfigNeigh-r10measSubframePattern-Neigh-r10 measSubframeCellList-r10

The MeasObjectEUTRA is more specifically described as follows.

TABLE 6 Description of MeasObjectEUTRA field carrierFreq identifies anE-UTRA carrier frequency effective in the configuration neighCellConfigindicates configuration information of a neighboring cell measCycleSCellParameter: Tmeasure_SCC is used when a secondary cell (SCell) operatesat a frequency indicated in the measObject and is in a non-activatedstate measSubframeCellList is a list of cells to which themeasSubframePattern-Neigh is applied. If a cell is not included in themeasSubframeCellList, a time domain measurement resource restrictionpattern for all neighboring cells is applied to the UEmeasSubframePattern-Neigh is a time domain measurement resourcerestriction pattern applied in measuring RSRP and RSRQ of a neighboringcell on the carrier frequency indicated in the carrierFreq

As described above, the MeasObjectEUTRA includes a configurationinformation of a neighboring cell (i.e., NeighCellConfig), a time domainmeasurement resource restriction pattern (i.e.,measSubframePattern-Neigh) applied in measuring RSRP and RSRQ of theneighboring cell, and a cell list (i.e., measSubframeCellList) to whichthe pattern is applied.

The time domain measurement resource restriction pattern configured forthe measured cell indicates at least one subframe per radio frame, usedfor performing measurement.

The measurement must not be performed in any subframe different fromthat indicated by the time domain measurement resource restrictionpattern for configured for the measured cell.

The configuration information of the neighboring cell (i.e.,NeighCellConfig) includes information related to the MBSFN of theneighboring cell and information related to TDD UL/DL configuration.

TABLE 7 Description of NeighCellConfig field neighCellConfig: is used toprovide information related to the MBSFN of the neighboring cell andinformation related to TDD UL/DL configuration 00: Although allneighboring cells are not applied at a specific frequency, some of theneighboring cells have the same MBSFN subframe allocation configurationas the serving cell. 10: All the neighboring cells have the same MBSFNsubframe allocation configuration as the serving cell at the specificfrequency. 01: All the neighboring cells do not have MBSFN subframeconfiguration. 11: When comparing the neighboring cell with the servingcell at the specific frequency, the neighboring cell has a differentUL/DL configuration from the serving cell.

FIG. 19 illustrates an example of a time domain measurement resourcerestriction pattern.

As can be seen with reference to FIG. 19(a), the time domain measurementresource restriction pattern (i.e., measSubframePatternPCell ormeasSubframePattern-Neigh) may be a subframe to which restriction isapplied or a subframe to which restriction is not applied, when the UE100 performs measurement. In this case, the subframe used to perform themeasurement by applying the restriction may be represented as 1, and thesubframe used to perform the measurement by not applying the restrictionmay be represented as 0.

FIG. 20 is an exemplary diagram illustrating a process of measuring RSRPand RSRQ.

Referring to FIG. 20(a), the UE 100 exists within the coverage of a picocell 300 and the coverage of a first macro cell (eNodeB) 221 and asecond macro cell (eNodeB) 222. In this case, the pico cell 300 is aserving cell, and the first and second macro cells (eNodeBs) 221 and 222are neighboring cells.

In this situation, a subframe that the pico cell 300 configures as anMBSFN is shown in FIG. 20(b). If the pico cell 300 configures thecorresponding subframe as the MBSFN and informs the first and secondmacro cells (eNodeBs) 221 and 222 of the configuration through the X2interface, the first and second macro cells 221 and 222 operate thecorresponding subframe as an ABS.

The pico cell 300 performs data transmission in the data region of thecorresponding subframe, and transmits CRSs in the control and dataregions. The CRSs are transmitted on zeroth, fourth, seventh andeleventh symbols. On the other hand, since the first and second macrocells 221 and 222 operate the corresponding subframe as the ABS, anydata is not transmitted in the data region, thereby preventinginterference between the CRSs. However, the first and second macro cells221 and 222 transmit CRSs on the zeroth, fourth, seventh and eleventhsymbols or the zeroth symbol according to the non-MBSFN ABS and MBSFNABS.

Meanwhile, the UE 100 receives, as described above, the radio resourceconfiguration dedicated IE and the measurement configuration(MeasConfig) from the pico cell 300.

In this case, the radio resource configuration dedicated IE includes themeasSubframePattern-Serv as described above. As described above, themeasurement configuration (MeasConfig) the neighCellConfig indicatingthe configuration information of the neighboring cell, themeasSubframePattern-Neigh indicating the time domain measurementresource restriction pattern applied in measuring the RSRP and RSRQ ofthe neighboring cell and the measSubframeCellList indicating the list ofthe cells to which the measSubframePattern-Neigh is applied.

First, the UE 100 identifies the measSubframePattern-Serv so as toperform measurement for the serving cell, i.e., the pico cell 300. If itis identified by the measSubframePattern-Serv that the received subframeis a subframe to which the restriction pattern is applied, the UE 100performs measurement by receiving CRSs on the zeroth, fourth, seventhand eleventh symbols of the subframe received from the serving cell,i.e., the pico cell 300.

Meanwhile, the UE 100 identifies the measurement configuration(MeasConfig) so as to measure the neighboring cells, i.e., the first andsecond macro cells 221 and 222. It is assumed that the subframe shown inFIG. 20(b) by the measSubframePattern-Neigh in the measurementconfiguration (MeasConfig) is a subframe to which the restriction isapplied in performing the measurement of the neighboring cell and thecells to which the restriction is applied by the measSubframeCellListare known as the first and second macro cells 221 and 222.

As such, when the subframe shown in FIG. 20(b) by themeasSubframePattern-Serv and the measSubframePattern-Neigh is a subframeto be measured, the UE 100 receives CRSs from the serving cell, i.e.,the pico cell 300, and receives CRSs from the neighboring cells, i.e.,the first and second macro cells 221 and 222, thereby performing themeasurement.

In this case, the subframe is operated as the ABS by the neighboringcells, i.e., the first and second macro cells 221 and 222, andtherefore, any data is not received in the data region.

When the RSRP and RSRQ are measured, the RSRQ depends on asignal-to-interference plus noise ratio (SINR). That is, the RSRQ isdefined as (NxSRP)/received signal strength indicator (RSSI). Here, Ndenotes a number of RBs in an RSSI measurement band, and RSSI denotes astrength of the received signal. That is, the RSRQ means the strength ofan actual reference signal by removing interference and noise from thereceived signal.

When the subframe shown in FIG. 20(b) is operated as the ABS by theneighboring cells, i.e., the first and second macro cells 221 and 222,and therefore, any data is not transmitted in the data region, the RSRQsof the serving cell and the neighboring cell are measured almostidentical to each other, and it cannot be determined which one of theserving cell and the neighboring cell has RSRQ superior to the other. Asa result, the UE cannot correctly perform cell selection or cellreselection.

When the subframes restricted by the measSubframePattern-Serve and themeasSubframePattern-Neigh are set identical to each other, there is aserious limitation in performing the cell selection or cell reselectionthrough RSRP and RSRQ.

Hereinafter, the accuracy required to measure RSRP and RSRQ will bedescribed.

The accuracy of the RSRP may be divided into absolute accuracy andrelative accuracy. The absolute accuracy and the relative accuracy willbe described in detail as follows.

First, the absolute accuracy will be described. When a time domainmeasurement resource pattern is applied, the absolute accuracy of theRSRP is required to measure a cell operating at the same frequency asthe serving cell.

If it is assumed that CRSs in the measured cell are transmitted fromone, two or four antenna ports, the required absolute accuracy is asfollows.

RSRP|_(dBm)≧−127 dBm with respect to bands 1, 4, 6, 10, 11, 18, 19, 21,24, 33, 34, 35, 36, 37, 38, 39, 40, 42 and 43

RSRP|_(dBm)≧−126 dBm with respect to bands 9 and 41

RSRP|_(dBm)≧−125 dBm with respect to bands 2, 5 and 7

RSRP|_(dBm)≧−124 dBm with respect to bands 3, 8, 12, 13, 14, 17 and 20

These are shown in the following Table 8.

TABLE 8 Condition Bands 1, 4, 6, 10, 11, 18, 19, 21, 24, 33, 34, 35, 36,37, Bands 3, Accuracy [dB] 38, 39, 8, 12, 13, General Maximum 40, 42Bands 2, 14, 17 Bands 9 Parameter Unit condition condition and 43 5 and7 and 20 and 41 Io Io Io Io RSRP for dBm ±6  ±9 121 dBm/ 119 dBm/ 118dBm/ 120 dBm/ Es/I_(ot) ≧ 15 kHz 15 kHz 15 kHz 15 kHz [−4] dB . . . - .. . - . . . - . . . - 70 dBm/ 70 dBm/ 70 dBm/ 70 dBm/ BW_(Channel)BW_(Channel) BW_(Channel) BW_(Channel) −70 dBm/ −70 dBm/ −70 dBm/ −70dBm/ RSRP for dBm ±9 ±11 BW_(Channel) BW_(Channel) BW_(Channel)BW_(Channel) Es/I_(ot) ≧ . . . - . . . - . . . - . . . - [−4] dB 50 dBm/50 dBm/ 50 dBm/ 50 dBm/ BW_(Channel) BW_(Channel) BW_(Channel)BW_(Channel)

Io is defined with respect to REs in the subframe indicated by the timedomain measurement resource restriction pattern applied in measuring theRSRP of the measured cell.

Meanwhile, when the time domain measurement resource pattern is applied,the relative accuracy of the RSRP is also required to measure a celloperating at the same frequency as the serving cell.

If it is assumed that CRSs in the measured cell are transmitted fromone, two or four antenna ports, the required relative accuracy is asfollows.

RSRP1,2|_(dBm)≧−127 dBm with respect to bands 1, 4, 6, 10, 11, 18, 19,21, 24, 33, 34, 35, 36, 37, 38, 39, 40, 42 and 43

RSRP1,2|_(dBm)≧−126 dBm with respect to bands 9 and 41

RSRP1,2|_(dBm)≧−125 dBm with respect to bands 2, 5 and 7

RSRP1,2|_(dBm)≧−124 dBm with respect to bands 3, 8, 12, 13, 14, 17 and20

Here, dBm is a unit of electric power (Watt), and 1 mW=0 dBm.

These are shown in the following Table 9.

TABLE 9 Condition Bands 1, 4, 6, 10, 11, 18, 19, 21, 24, 33, 34, 35, 36,37, Bands 3, Accuracy [dB] 38, 39, 8, 12, 13, General Maximum 40, 42Bands 2, 14, 17 Bands 9 Parameter Unit condition condition and 43 5 and7 and 20 and 41 Io Io Io Io RSRP for dBm ±2 ±3 −121 dBm/ −119 dBm/ −118dBm/ −120 dBm/ Es/I_(ot) ≧ 15 kHz 15 kHz 15 kHz 15 kHz [−4] dB . . . - .. . - . . . - . . . - 50 dBm/ 50 dBm/ 50 dBm/ 50 dBm/ BW_(Channel)BW_(Channel) BW_(Channel) BW_(Channel) RSRP for dBm ±3 ±3 −121 dBm/ −119dBm/ −118 dBm/ −120 dBm/ Es/I_(ot) ≧ 15 kHz 15 kHz 15 kHz 15kHz [−4] dB. . . - . . . - . . . - . . . - 50 dBm/ 50 dBm/ 50 dBm/ 50 dBm/BW_(Channel) BW_(Channel) BW_(Channel) BW_(Channel)

Hereinafter, the accuracy of the RSRQ will be described.

When a time domain measurement resource pattern is applied, the absoluteaccuracy of the RSRQ is also required to measure a cell operating at thesame frequency as the serving cell.

If it is assumed that CRSs in the measured cell are transmitted fromone, two or four antenna ports, the required absolute accuracy is asfollows.

RSRQ|_(dBm)≧−127 dBm with respect to bands 1, 4, 6, 10, 11, 18, 19, 21,24, 33, 34, 35, 36, 37, 38, 39, 40, 42 and 43

RSRQ|_(dBm)≧−126 dBm with respect to bands 9 and 41

RSRQ|_(dBm)≧−125 dBm with respect to bands 2, 5 and 7

RSRQ|_(dBm)≧−124 dBm with respect to bands 3, 8, 12, 13, 14, 17 and 20

These are shown in the following Table 10.

TABLE 10 Condition Bands 1, 4, 6, 10, 11, 18, 19, 21, 24, 33, 34, 35.36, 37, Bands 3, Accuracy [dB] 38, 39, 8, 12, 13, General Maximum 40, 42Bands 2, 14, 17 Bands 9 Parameter Unit condition condition and 43 5 and7 and 20 and 41 Io Io Io Io RSRQ dBm ±2.5 ±4 −121 dBm/ −119 dBm/ −118dBm/ −120 dBm/ when 15 kHz 15 kHz 15 kHz 15 kHz RSRP . . . - . . . - . .. - . . . - Es/I_(ot) = 50 dBm/ 50 dBm/ 50 dBm/ 50 dBm/ [TBD] dBBW_(Channel) BW_(Channel) BW_(Channel) BW_(Channel) RSRQ dBm ±3.5 ±4−121 dBm/ −119 dBm/ −118 dBm/ −120 dBm/ when 15 kHz 15 kHz 15 kHz 15 kHzRSRP . . . - . . . - . . . - . . . - Es/I_(ot) = 50 dBm/ 50 dBm/ 50 dBm/50 dBm/ [−4] dB BW_(Channel) BW_(Channel) BW_(Channel) BW_(Channel)

As described above, the UE necessarily measures the RSRQ in only thesubframe indicated by the measSubframePattern-Serv and themeasSubframePattern-Neigh. Although the RSRP may be measured in anothersubframe, the measurement is generally performed on only the indicatedsubframe for the purpose of actual requirements.

FIG. 21 is an exemplary diagram illustrating a situation in which a UEexists within a coverage of the pico cell 300 and a coverage of themacro cell (eNodeB) 220.

As can be seen with reference to FIG. 21, when the macro cell 220operates a specific subframe as the ABS under a situation in which themacro cell and the pico cell coexist, the UE 100 performs cell selectionor cell reselection by measuring the signal strength and quality of eachcell in the corresponding specific subframe.

In this case, two scenarios may exist. A first scenario is a case inwhich the macro cell 200 is a serving cell and the pico cell 300 is aneighboring cell. A second scenario is a case in which the pico cell 300is a serving cell and the macro cell is a neighboring cell.

First, the first scenario is shown in FIG. 21(a). As shown in FIG.21(a), the UE 100 is under communication with the macro cell 220 that isa serving cell, and measures RSRP and RSRQ by receiving CRSs from themacro cell 220 and the pico cell 300 while moving toward the macro cell220. Accordingly, the UE 100 finally performs selection or reselectionof the pico cell 300.

Next, the second scenario is shown in FIG. 21(b). As shown in FIG.21(b), the UE 100 is under communication with the pico cell 300 that isa serving cell, and measures RSRP and RSRQ by receiving CRSs from themacro cell 220 and the pico cell 300 while moving the macro cell 220.Accordingly, the UE 100 finally performs selection or reselection of themacro cell 220.

As described above, when the subframe indicated by themeasSubframePattern-Serv and the measSubframePattern-Neigh is set to theABS by the macro cell 220, and therefore, any data is not received, theRSRQs of the serving cell and the neighboring cell are measured almostidentical to each other, and it cannot be determined which one of theserving cell and the neighboring cell has RSRQ superior to the other. Asa result, the UE cannot correctly perform cell selection or cellreselection.

Although the UE measures an actual RSRP/RSRQ of the macro cell 220 in asubframe set to the ABS by the macro cell 200, an actual service is notperformed in the period of the corresponding subframe. Hence, it ismeaningless that the UE performs cell selection or cell reselection.

Hereinafter, a method in which a serving cell and a neighboring celldifferently configure the time domain measurement resource limitationpattern indicating subframes to be measured will be described.

FIG. 22 illustrates an example in which subframes for cell measurementare differently configured under a situation in which the macro cell andpico/femto cells coexist.

In FIG. 22, when the macro cell 220 is a serving cell, the macro cell220 and the pico cell 300 differently configure subframes formeasurement.

Specifically, the macro cell 220 configures zeroth and eighth subframesamong subframes 2201 as ABSs. In this case, a pattern representing ageneral subframe other than the ABS, i.e., a non-ABS pattern 2202 may berepresented as 0111111101111111. In addition, a pattern representing thesubframe configured as the ABS, i.e., an ABS pattern 2203 may berepresented as 1000000010000000.

In this case, like the macro cell 220, the pico cell 300 that is aneighboring cell may configure subframes as ABSs. However, the macrocell 220 and the pico cell 300 necessarily configure different timedomain measurement resource restriction patterns indicating subframes tobe measured.

That is, the time domain measurement resource restriction pattern (i.e.,the measSubframePattern-Serv) applied in performing measurement on themacro cell 220 that is the serving cell is a subset of the non-ABSpattern 2202, and may be configured as 0110000001100000.

The time domain measurement resource restriction pattern (i.e., themeasSubframePattern-Neigh) applied in performing measurement on the picocell 300 that is the neighboring cell is a subset of the ABS pattern2203, and may be configured as 1000000010000000.

As such, the macro cell 220 and the pico cell 300 differently configurethe time domain measurement resource restriction patterns indicating thesubframes to be measured, thereby solving the aforementioned problem.

FIG. 23 illustrates another example in which the subframes for cellmeasurement are configured differently in the situation in which themacro cell and the pico/femto cells coexist.

In FIG. 23, when the pico cell 300 is a serving cell, the macro cell 220and the pico cell 300 differently configure subframes for measurement.

Specifically, the macro cell 220 that is a neighboring cell configureszeroth and eighth subframes among subframes 2301 as ABSs. In this case,a pattern representing a general subframe other than the ABS, i.e., anon-ABS pattern 2302 may be represented as 0111111101111111. Inaddition, a pattern representing the subframe configured as the ABS,i.e., an ABS pattern 2303 may be represented as 1000000010000000.

In this case, like the macro cell 220 that is the neighboring cell, thepico cell 300 that is the serving cell may configure subframes as ABSs.However, the macro cell 220 and the pico cell 300 necessarily configuredifferent time domain measurement resource restriction patternsindicating subframes to be measured.

That is, the time domain measurement resource restriction pattern (i.e.,the measSubframePattern-Serv) applied in performing measurement on thepico cell 300 that is the serving cell is a subset of the ABS pattern2303, and may be configured as 1000000010000000.

The time domain measurement resource restriction pattern (i.e., themeasSubframePattern-Neigh) applied in performing measurement on themacro cell 220 that is the neighboring cell is a subset of the non-ABSpattern 2302, and may he configured as 0110000001100000.

According to the method of the present invention shown in FIGS. 22 and23, when the macro cell 220 is a serving cell or neighboring cell, thepattern for the RSRP/RSRQ measurement of the macro cell 220 is limitedto the subset of a subframe except the ABS subframe of the macro cell220. On the other hand, the pattern for the RSRP/RSRQ measurement of thepico cell 300 is identical to the ABS subframe of the macro cell 220 oris limited to the subset of a subframe except the ABS subframe of themacro cell 220.

As such, the macro cell 220 and the pico cell 300 differently configurethe time domain measurement resource restriction patterns indicating thesubframes to be measured, thereby solving the aforementioned problem.

Particularly, the absolute accuracy obtained by measuring RSRQs usingparameters shown in the following Table 11 under a non-MBSFN situationin which CRSs do not collide with one another is shown in the followingTable 11.

In the following Table 11, Cell 1 is a serving cell and Cell 2 is atarget cell. The RSSI is used for RSRQ. The RSRQ is a cell indicated bythe time domain measurement resource restriction pattern configured forthe measured cell. In addition, RSSI is used for the RSRQ.

TABLE 11 Test 1 Test 2 Test 3 Parameter Unit Cell 1 Cell 2 Cell 1 Cell 2Cell 1 Cell 2 E-UTRA RF 1 1 1 Channel Number BW_(Channel) MHz 10 10 10Reference Signals mod(PCI_(cell1),3) mod(PCI_(cell1),3)mod(PCI_(cell1),3) ! = mod(PCI_(cell2),3) ! = mod(PCI_(cell2),3) ! =mod(PCI_(cell2),3) Cell ABS pattern [1100 N/A [1100 N/A [1100 N/A 000]0000] 0000] ABS pattern for [00110000] [00110000] [00110000] servingcell measurement signaled to the UE in measSubframe Pattern-Serv-r10 ABSpattern for [11000000] [11000000] [111000000] neighbor cell measurementsignaled to the UE in measSubframe Pattern-Neigh-r10 Measurement n_(PRB)22-7 22-7 22-7 bandwidth PDSCH Reference R.O — R.O — R.O — measurementFDD FDD FDD channel PDSCH allocation n_(PRB) 13-6 — 13-6 — 13-6 —PDCCH/PCFICH/ R.6 FDD R.6 FDD R.6 FDD PHICH Reference measurementchannel OCNG Patterns OP.1 OP.2 OP.1 OP.2 OP.1 OP.2 (OP.1 FDD) and FDDFDD FDD FDD FDD FDD A.3.2.1.2 (OP.2 FDD) PBCH RA dB 0 0 0 0 0 0 PBCH RBPSS RA SSS RA PCFICH RB PHICH RA PHICH RB PDCCH RA PDCCH RB PDSCH RAPDSCH RB OCNG RA OCNG RB N_(oc) Bands 1. dBm/ [−84.76] [−84.76][−103.85] [−103.85] [−116] 4, 6, 10, 15 kHz 11, 18, 19, 21, 23 and 24Bands 2, [−114] 5 and 7 [112.5] Band 25 [−113] Bands 3, 8, 12, 13, 14,17 and 20 Band 9 [−115] Es/I_(ot) on Non-ABS dB [1.881] [−7.46] [1.881][−7.46] [2.541] [−9.46] subframe Es/I_(ot) on ABS dB [1.881] [−7.46][1.881] [−7.46] [2.541] [−4] subframe RSRP Bands 1, dBm/ [−80.76][−86.76] [−99.85] [−105.85] [−112] [−120] 4, 6, 10, 15 kHz 11, 18, 19,21. 23 and 24 Bands 2, [−110] [−118] 5 and 7 Band 25 [−108.5] [−116.5]Bands 3, [−109] [−117] 8, 12, 13, 14, 17 and 20 Band 9 [−111] [−119]RSRQ Bands 1, dB [−12.96] [−15.22] [−12.96] [−15.22] [−12.71] [−16.6] 4,6. 10, 11, 18, 19, 21, 23 and 24 Bands 2, 5, 7 and 25 Bands 3, 8, 12,13, 14, 17 and 20 Band 9 Io on Bands 1, dBm/ [−51] [−51] [−70] [−70][−82.3] Non- 4, 6, 10, 9 MHz ABS 11, 18, subframe 19, 21, 23 and 24Bands 2, [−80.3] 5 and 7 Band 25 [−78.8] Bands 3, [−79.3] 8, 12, 13, 14,17 and 20 Band 9 [−81.3] Io on Bands 1, dBm/ [−53.86] [−53.86] [−72.95][−72.95] [−85.6] ABS 4, 6, 10, 9 MHz subframe 11, 18, 19, 21, 23 and 24Bands 2, [−83.6] 5 and 7 Band 25 [−82.1] Bands 3, [−82.6] 8, 12, 13, 14,17 and 20 Band 9 [−84.6] Es/N_(oc) dB [4] [−2] [4] [−2] [4] [−4]Propagation — AWGN AWGN AWGN condition

In Table 11, the OCNG is used when cells are sufficiently allocated andthe total transmission power spectral density for OFDM symbols ismaintained constant. It was assumed that interference and noise sourcesfrom another cell not indicated in the test are constant with respect tosubcarriers. The RSRQ, RSRP and Io level are induced from anotherparameter for another information. The minimum requirements of the RSRPand RSRQ are indicated under the assumption that the subcarriers have norelation with interference and noise in the antenna port of eachreceiver. It is assumed that PDSCH is not transmitted in the ABSsubframe.

Meanwhile, the absolute accuracy obtained by measuring RSRQs usingparameters shown in the following Table 12 under an MBSFN ABS situationis shown in the following Table 12.

TABLE 12 Test 1 Test 2 Test 3 Parameter Unit Cell 1 Cell 2 Cell 1 Cell 2Cell 1 Cell 2 E-UTRA RF 1 1 1 Channel Number BW_(Channel) MHz 10 10 10Reference Signals mod(PCI_(cell1),3) = mod(PCI_(cell1),3) =mod(PCI_(cell1),3) = mod(PCI_(cell2),3) mod(PCI_(cell2),3)mod(PCI_(cell2),3) Cell ABS pattern [0010 N/A [0010 N/A [0010 N/A 0001000010 00010 00010 00010 00010 00000 00000 00000] 0] 0] ABS pattern for[010000100001 [010000100001 [010000100001 serving cell 00000000]00000000] 00000000] measurement signaled to the UE in measSubframePattern-Serv-r10 ABS pattern for [001000010000 [001000010000[001000010000 neighbor cell 10000000] 10000000] 10000000] measurementsignaled to the UE in measSubframe Pattern-Neigh-r10 Measurement n_(PRB)22-7 22-7 22-7 bandwidth PDSCH Reference R.O — R.O — R.O — measurementFDD FDD FDD channel PDSCH allocation n_(PRB) 13-6 — 13-6 — 13-6 —PDCCH/PCFICH/ R.6 FDD R.6 FDD R.6 FDD PHICH Reference measurementchannel OCNG Patterns OP.1 OP.2 OP.1 OP.2 OP.1 OP.2 (OP.1 FDD) and FDDFDD FDD FDD FDD FDD A.3.2.1.2 (OP.2 FDD) PBCH RA dB 0 0 0 0 0 0 PBCH RBPSS RA SSS RA PCFICH RB PHICH RA PHICH RB PDCCH RA PDCCH RB PDSCH RAPDSCH RB OCNG RA OCNG RB N_(oc) Bands 1, dBm/ [−84.76] [−84.76][−103.85] [−103.85] [−116] 4, 6, 10, 15 kHz 11, 18, 19, 21, 23 and 24Bands 2, [−114] 5 and 7 Band 25 [112.5] Bands 3, [−113] 8, 12, 13, 14,17 and 20 Band 9 [−115] Es/I_(ot) on Non-ABS dB [1.881] [−7.46] [1.881][−7.46] [2.541] [−9.46] subframe Es/I_(ot) on ABS dB [1.881] [−2][1.881] [−2] [2.541] [−4] subframe RSRP Bands 1, dBm/ [−80.76] [−86.76][−99.85] [−105.85] [−112] [−120] 4, 6, 10, 15 kHz 11,18, 19, 21, 23 and24 Bands 2, [−110] [−118] 5 and 7 Band 25 [−108.5] [−116.5] Bands 3,[−109] [−117] 8, 12, 13, 14, 17 and 20 Band 9 [−111] [−119] RSRQ Bands1, dB [−12.96] [−15] [−12.96] [−15] [−12.71] [−16.34] 4, 6, 10, 11, 18,19, 21, 23 and 24 Bands 2, 5, 7 and 25 Bands 3, 8, 12, 13, 14, 17 and 20Band 9 Io on Bands 1, dBm/ [−51] [−51] [−70] [−70] [−82.3] Non- 4, 6,10, 9 MHz ABS 11, 18, subframe 19, 21, 23 and 24 Bands 2, [−80.3] 5 and7 Band 25 [−78.8] Bands 3, [−79.3] 8, 12, 13, 14, 17 and 20 Band 9[−81.3] Io on Bands 1, dBm/ [−53.86] [−53.86] [−72.95] [−72.95] [−85.6]ABS 4, 6, 10, 9 MHz subframe 11, 18, 19, 21, 23 and 24 Bands 2, [−83.6]5 and 7 Band 25 [−82.1] Bands 3, 8, 12, 13, 44, 17 [−82.6] and 20 Band 9[−84.6] Es/N_(oc) dB [4] [−2] [4] [−2] [4] [−4] Propagation — AWGN AWGNAWGN condition Time offset between ms [2] [2] [2] cells

The exemplary embodiments described above may be implemented usingvarious means. For example, the exemplary embodiments may be implementedby hardware, firmware, software, or combination thereof.

According to the implementation using the hardware, the method accordingto the exemplary embodiments may be implemented using at least one ofapplication specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, etc.

According to the implementation using the firmware or software, themethod according to the exemplary embodiments may be implemented in theform of a module, procedure or function performing functions andoperations described above. Software codes may be stored in a memoryunit and executed by a processor. The memory unit may be located in theinside or outside of the processor, and communicate data with theprocessor using various means known in the art.

FIG. 24 is a configuration block diagram illustrating the UE 100 and theBS 220/300 according to an exemplary embodiment.

As shown in FIG. 24, the UE 100 includes a storage means 110, acontroller 120 and a transceiver 130. The BS 220/300 is a macro BS orpico/femto BS, and includes a storage means 221/301, a controller222/302 and a transceiver 223/303.

The storage means 110 or 221/301 stores the methods shown in FIGS. 10 to23. The transceiver 130 or 223/303 transmits/receive the aforementionedsignals.

The controller 120 or 222/302 controls the storage means and thetransceiver. Specifically, each of the controllers performs the methodsstored in the storage means.

According to the exemplary embodiments, it is possible to increase theaccuracy in measuring the RSRP and RSRQ and to reduce measurement time.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present disclosure. The presentteachings can be readily applied to other types of apparatuses. Thisdescription is intended to be illustrative, and not to limit the scopeof the claims. Many alternatives, modifications, and variations will beapparent to those skilled in the art. The features, structures, methods,and other characteristics of the exemplary embodiments described hereinmay be combined in various ways to obtain additional and/or alternativeexemplary embodiments.

As the present features may be embodied in several forms withoutdeparting from the characteristics thereof, it should also be understoodthat the above-described embodiments are not limited by any of thedetails of the foregoing description, unless otherwise specified, butrather should be construed broadly within its scope as defined in theappended claims, and therefore all changes and modifications that fallwithin the and bounds of the claims, or equivalents of such metes andbounds are therefore intended to be embraced by the appended claims.

What is claimed is:
 1. A method for transmitting, by a base station of aserving cell, information for cell measurements, the method comprising:transmitting, by the base station, signals according to an almost blanksubframe pattern; and transmitting, by the base station, informationindicating a first time domain measurement source restriction patternconfigured for the serving cell and information indicating a second timedomain measurement resource restriction pattern configured for aneighbor cell, wherein the almost blank subframe pattern indicates whichsubframes among subframes corresponding to the almost blank subframepattern the base station is configuring as almost blank subframes or asnon-almost blank subframes, wherein the first time domain measurementresource restriction pattern indicates which subframe among subframescorresponding to the first time domain measurement resource restrictionpattern is one or more first subframes configured for reference signalreceived power (RSRP) or reference signal received quality (RSRQ)measurements of the serving cell, and the second time domain measurementresource restriction pattern indicates which subframe among subframescorresponding to the second time domain measurement resource restrictionpattern is one or more second subframes configured for RSRP or RSRQmeasurements of the neighbor cell, wherein the first time domainmeasurement resource restriction pattern is configured such that the oneor more first subframes are a subset of the non-almost blank subframesindicated by the almost blank subframe pattern, and wherein the secondtime domain measurement resource restriction pattern is configured suchthat the one or more second subframes are a subset of the almost blanksubframes indicated by the almost blank subframe pattern.
 2. The methodof claim 1, further comprising: transmitting, by the base station,information indicating the almost blank subframe pattern to a basestation of the neighbor cell.
 3. The method of claim 2, wherein theinformation indicating the almost blank subframe pattern is transmittedto the base station of the neighbor cell via a X2 interface.
 4. Themethod of claim 1, wherein each of the first and second time domainmeasurement resource restriction patterns indicates at least onesubframe per a radio frame for the RSRP or RSRQ measurement.
 5. Themethod of claim 1, wherein the information indicating the first timedomain measurement resource restriction pattern and the informationindicating the second time domain measurement resource restrictionpattern is transmitted via a radio resource control message.
 6. Themethod of claim 1, wherein the almost blank subframe pattern is appliedrepeatedly.
 7. A method for performing, by a user equipment, cellmeasurements, the method comprising: receiving, by the user equipment,information indicating a first time domain measurement resourcerestriction pattern configured for a serving cell and informationindicating a second time domain measurement resource restriction patternconfigured for a neighbor cell; and performing, by the user equipment,reference signal received power (RSRP) or reference signal receivedquality (RSRQ) measurements of the serving cell in one or more firstsubframes based on the first time domain measurement resource pattern,and RSRP or RSRQ measurements of the neighbor cell in one or more secondsubframes based on the second time domain measurement resource pattern,wherein the first time domain measurement resource restriction patternindicates which subframe among subframes corresponding to the first timedomain measurement resource restriction pattern is the one or more firstsubframes configured for the RSRP or RSRQ measurements of the servingcell, and the second time domain measurement resource restrictionpattern indicates which subframe among subframes corresponding to thesecond time domain measurement resource restriction pattern is the oneor more second subframes configured for the RSRP or RSRQ measurements ofthe neighbor cell, wherein the first time domain measurement resourcerestriction pattern is configured such that the one or more firstsubframes are a subset of non-almost blank subframes among subframescorresponding to an almost blank subframe pattern, and the almost blanksubframe pattern indicates which subframes a base station is configuringas almost blank subframes or as the non-almost blank subframes, andwherein the second time domain measurement resource restriction patternis configured such that the one or more second subframes are a subset ofthe almost blank subframes indicated by the almost blank subframepattern.
 8. The method of claim 7, wherein each of the first and secondtime domain measurement resource restriction patterns indicates at leastone subframe per a radio frame for the RSRP or RSRQ measurements.
 9. Themethod of claim 7, wherein the information indicating the first timedomain measurement resource restriction pattern and the informationindicating the second time domain measurement resource restrictionpattern is received via a radio resource control message.
 10. A basestation for transmitting information for cell measurements, the basestation comprising: a transmitter, and a processor configured to controlthe transmitter, the processor further configured to: control thetransmitter to transmit signals according to an almost blank subframepattern, and control the transmitter to transmit information indicatinga first time domain measurement resource restriction pattern configuredfor a serving cell and information indicating a second time domainmeasurement resource restriction pattern configured for a neighbor cell,wherein the almost blank subframe pattern indicates which subframesamong subframes corresponding to the almost blank subframe pattern thebase station is configuring as almost blank subframes or as non-almostblank subframes on the serving cell, wherein the first time domainmeasurement resource restriction pattern indicates which subframe amongsubframes corresponding to the first time domain measurement resourcerestriction pattern is one or more first subframes configured forreference signal received power (RSRP) or reference signal receivedquality (RSRQ) measurements of the serving cell, and the second timedomain measurement resource restriction pattern indicates which subframeamong subframes corresponding to the second time domain measurementresource restriction pattern is one or more second subframes configuredfor RSRP or RSRQ measurements of the neighbor cell, wherein the firsttime domain measurement resource restriction pattern is configured suchthat the one or more first subframes are a subset of the non-almostblank subframes indicated by the almost blank subframe pattern, andwherein the second time domain measurement resource restriction patternis configured such that the one or more second subframes are a subset ofthe almost blank subframes indicated by the almost blank subframepattern.
 11. The base station of claim 10, wherein the processor isfurther configured to control the transmitter to transmit informationindicating the almost blank subframe pattern to a base station of theneighbor cell.
 12. The base station of claim 11, wherein the informationindicating the almost blank subframe pattern is transmitted to the basestation of the neighbor cell via a X2 interface.
 13. The base station ofclaim 10, wherein each of the first and second time domain measurementresource restriction pattern indicates at least one subframe per a radioframe for the RSRP or RSRQ measurements.
 14. The base station of claim10, wherein the information indicating the first time domain measurementresource restriction patterns and the information indicating the secondtime domain measurement resource restriction pattern is transmitted viaa radio resource control message.
 15. The base station of claim 10,wherein the almost blank subframe pattern is applied repeatedly.
 16. Auser equipment for performing cell measurements, the user equipmentcomprising: a receiver, and a processor configured to control thereceiver, the processor further configured to: control the receiver toreceive information indicating a first time domain measurement resourcerestriction pattern configured for a serving cell and informationindicating a second time domain measurement resource restriction patternconfigured for a neighbor cell, and perform reference signal receivedpower (RSRP) or reference signal received quality (RSRQ) measurements ofthe serving cell in one or more first subframes based on the first timedomain measurement resource pattern, and RSRP or RSRQ measurements ofthe neighbor cell in one or more second subframes based on the secondtime domain measurement resource pattern, wherein the first time domainmeasurement resource restriction pattern indicates which subframe amongsubframes corresponding to the first time domain measurement resourcerestriction pattern is the one or more first subframes configured forthe RSRP or RSRQ measurements of the serving cell, and the second timedomain measurement resource restriction pattern indicates which subframeamong subframes corresponding to the second time domain measurementresource restriction pattern is the one or more second subframesconfigured for the RSRP or RSRQ measurements of the neighbor cell,wherein the first time domain measurement resource restriction patternis configured such that the one or more first subframes are a subset ofnon-almost blank subframes among subframes corresponding to an almostblank subframe pattern, and the almost blank subframe pattern indicateswhich subframes a base station is configuring as almost blank subframesor as the non-almost blank subframes, and wherein the second time domainmeasurement resource restriction pattern is configured such that the oneor more second subframes are a subset of the almost blank subframesindicated by the almost blank subframe pattern.
 17. The user equipmentof claim 16, wherein each of the first and second time domainmeasurement resource restriction patterns indicates at least onesubframe per a radio frame for the RSRP or RSRQ measurements.
 18. Theuser equipment of claim 16, wherein the information indicating the firsttime domain measurement resource restriction pattern and the informationindicating the second time domain measurement resource restrictionpattern is received via a radio resource control message.